Vitreous enameling



Patented Jan. 18, 1944 vrmn'ous ENAMELING Leon J. Frost and Charles H. Commons, In, Niagara Falls, N. Y., assignors to The Titanium Alloy Manufacturing Company, New .York, N. Y., a corporation of Maine No Drawing. Application March 11, 1942, Serial No. 434,292

9 Claims. (Cl. 106- 48) This invention relates to frit compositibns for use in preparing vitreous enamels. This application is a continuation-impart of our copending application Serial No. 292,874, filed August 31, 1939.

In recent years, an important development in the field of vitreous enameling has been with reference to enamel compositions containing zircon zirconium silicate, zirconium oxide or other zirconium compounds in the raw frit batch. An important advantage of the use of such zirconium compounds in enamels is that enamels containing them do not require the presence of antimony or other poisonous compounds to secure the required opacity. These enameling frit compositions, particularly when opacified with zirconium oxide and milled to form suitable slips, and fired on a suitable base, form enamels of high opacity. However, among other problems connected with the preparation of such frits is that of acid resistance, particularly when used for such purposes as kitchen ware, hospital utensils and the like.

composition is provided which contains zircon or other zirconium compound and a small amount of the lithium containing mineral amblygonite. This frit composition is smelted, and then milled with an opacifier and other ingredients in customary fashion to form a slip, which is then applied to a suitable surface and fired to form an enamel.

Amblygonite is a complex fluoride-phosphate of lithium and aluminum. This mineral contains about 80 per cent A120: plus P205, with 5 to 9 per cent L120 and most of the remainder fluorine, with minor amounts -of impurities. By some it has been designated as a material containing aluminum phosphate, and when the term "aluminum phosphate is mentioned in the claims, it is understood that amblygonite is included. At any rate, its use in enamels is-high- 1y advantageous as a relatively cheap source of lithium, and in addition furnishes fluorine, P11057- phorus and aluminum, which are desired enamel ingredients, at least in small amounts. Lithium compounds in enamels act as fluxes, and in this respect are much powerful than compounds of the other alkali metals such as sodium and potassium. Thus 0.2% of lithium is about as effective as 1% of sodium. In addition, lithium com pounds have a less deleterious eifect upon the acid resistance of enamels in which they are incorporated than the corresponding compounds of so- In accordance with this invention, a raw frit dium and potassium. The net result is that enamels in which lithium replaces an equivalent part of the sodium or potassium employed as fluxes exhibit improved acid resistance.

The amount of ambylgonite to be used is generally quite small, a convenient quantity being I about 2 per cent. The advantages gained by incorporating amblygonite generally decrease as the quantity is increased too much, principally because of the increased amount of P205 in the enamel. In general it has been found that amounts above 6 per cent are not desirable, and that amounts below about V4 to /2 of 1 per cent are not sumciently effective. The preferred amount is about 1 /2 to 2% per cent.

Amblygonite in this respect seems to have a superior effect to that of other lithium containing minerals, such as lepidolite and spodumene, or lithium compounds such as lithium carbonate. This is true even when the formula is adjusted so as tocontain the same amount of lithium, phosphate, aluminum and fluorine as is contained in amblygonite. 7

As stated above, in accordance with the present invention amblygonite is incorporated in trit compositions containing zirconium compounds. 01' the available zirconium com-pounds, zircon or zirconium silicate is the most suitable from the standpoint of cost and availability. The important thing, of course, is that the final frit should contain a certain amount of zirconium oxide, since zirconium silicate and other zirconium compounds apparently decompose during the process of smelting to form zirconium oxide, which in turn may recombine with other frit constituents. Zirconium oxide itself may be used. but is generally not preferred on account of cost. Certain so-called double zirconium silicatesysuch as calcium zirconium silicate, magnesium zirconium silicate, zinc zirconium silicate and others, as described in U. 8. Patent No.

2,127,844, present certain advantages when used in certain frit formulas. Modern zirconium containing trits generally contain from about 4 to 15 per cent ZrOa and preferably 6 to 12 per cent 210:. If zircon is used this would mean about 5 to 22.5 per cent zircon, or preferably 9 to 18 per cent zircon. The present invention 'may thus be used not only with enamels of the type described in our copending application Serial No. 292,874 of which this is a continuation-in-part, but also in other enamels.

The invention having been described generally,

types of zirconium-containing iier, 0.1 part of of enamelers clay, parts of the following examples are given of specific modes of practicing the same:-

EXAMIPLEI Dehydrated borax 23.12 Pyrophyllite 38.46 Zircon 15.38 F'luorspar 6.00 Zinc oxide 2.78 Amblygonite I 2.00 Sodium silicofluoride .l 12.03 Sodium nitr 2.50 Aluminum hydrate 2.90

100 parts of this frit were milled with 8 parts of enamelers clay, 6 parts of zirconium oxide opacifler, 1 part of zinc oxide, /4 part of sodium fluoride and about 40 parts of water to 4 grams residue per 100 cc. of slip on a 200 mesh sieve. The slip thus formed may be applied by dipping or spraying to sheet iron, previously supplied with a ground coat, at any suitable rate in one Or two coats, according to standard practice in the enameling industry. After firing for 2 /2 minutes at i520 F., the surface is highly lustrous and of a good cream white color.

EXAMPLEZ' The following ingredients ,(given in parts by weight) were mixed together and smelted at a temperature of about 2100 Euntil a melt forming smooth strings results.

Dehydrated borax 100 parts of this frit were milled with 5 parts 0! enamelers clay, 6 parts of zirconium oxide opacisodium nitrite and about 40 parts of water to 3 grams residue per 100 cc. of slip on a 200 mesh sieve. The slip thus formed may be applied as in Example 1. After firing EXAMPLES 4-1-1 The following examples were prepared by mixing the raw ingredients as shown by the table below, and smelting at a temperature of 2000 to 2100 F. until a melt forming smooth strings results.

Tum:

Parts by weight Examples Dehydrated borex 224. 5 221. 7 136. 3 219. 7 Sodium fluosilicate 116. 9 115. 3 100. 3 114. 3 Fluorspar 3 57. 5 54. 4 57. 0 Zinc oxide 2 20. 4 Amblygonite. 1 19. 0 Sodium nitrate 7 2.3. 8 Zircon 146. 2 Pyrophyllite 360. 0 Aluminum hydrate. 27. 8 Zinc zirconium silicat Special opaciiier Quartz powder Boric acid Zirconium spinel Sillimanite Andalusite English china clay .a 261. 3

Examples Dehydratedborax 219. 7 134. 6 221. 0 222. 3 Sodium fluosilicate 114. 3 100. 6 114. 9 115. 7 Fluorspar 57. 0 54. 6 57. 3 67. 7 Zinc oxide 25. 3 26. 5 Amblygonite 19. 0 18. 2 19. 1 l9. 2 Sodium nitrate 23. 8 22. 8 23. 9 24. 1

ircon 86. 1 03. 6 Pyrophylli 366. 0 350. 7 440. 1 334. 5 Aluminum 27. 8 26. 6 1. 7 Zinc zirconium silicate 86. 5 .Special opacifler 1 164. 5 Zirconium oxide 95. 5 58.3

"this product is a zirconium opaciiier produced in accordance with U. 5. Patent No. 1,789,311.

- 100 parts of each of these frits were each milled for 2 /2 minutes at 1500? F. theopacity, -gloss and surface are excellent.

The following ingredients (given in parts by weight) were mixed together and smelted at 2100* F. until a melt forming smooth strings results;

with 6 parts of enamelers clay, 6 parts of zirconium oxide, 0.1 part of NaNOz, and 38 parts of water to a fineness of +200 mesh. The slip thus formed was applied by spraying to sheet' iron, previously supplied with a ground coat, at the rate of 72 grams per sq. ft. for two coats. After firing at 1500 F. for 2 /2 to 4 minutes, the surfaces are highly lustrous and of a good cream white color.

1 nxmnn 12 The following ingredients (given in parts by weight) were mixed together and smelted at 2150 Quartz 32.74 Soda-ash 3.79 Sodium nitrate- 2.50 Cryolite 13.77 Fluorspar 5.17 Pyrophyllite 14.28 Zircon 10.78 Amblygonite 3.00

100 parts of this frit were milled with 7 parts rconium oxide opacifier, A part ofMgCO: and about 40 parts of water to 12 grams residue per 100 cc of slip 7 on a 200 mesh sieve.

results. i Dehydrated borax 18.78 Fluorspar 6.00 Calcium carbcnate ..s ,14.26 Titanium dioxide 4.00 Zircon 10.76 Sodium nitr 0.00 Sodium eilinnflunride 12.00 Soda ash 5.88- Amblygonite 2.00 Quartz 42.05 parts of this frit were milled with 5 parts to 2200 F..unti1 a melt forming smooth strings of enamelers clay, 6 parts of zirconium oxide opacifier, 0.1 part of sodium nitrite and about 4 5- parts of water to 1 gram residue per 100 cc.-.of

slip on a 200 mesh sieve. Although the opacity was not very high, the acid resistance was very good.

EXAMPLE 13 The following ingredients (given in parts by weight) were mixed together and smelted at 2100 F. until a melt forming smooth strings results.

Dehydrated borax 14.45

Calcium carbonate 14.93 Titanium dioxide 7.32 Zircon 9.85 Sodium nitr 5.00 Sodium silicofluoride 12.00 Soda ash 10.30 Quartz 38.43 Amblygonite 1.84

The following ingredient (parts by weight) were mixed together and smelted in customary fashion at a temperature of 2050f-2l00 F.

Dehydrated borax 17.67 Quartz 36.80 Soda ash 5.30 Sodium siliccfluoride 11.28 Calcium fluor 5.64 Titanium oxide 4.70 Amblygonite 1.88 Sodium nitrate 5.00 Calcium carbonate 8.39

Calcium zirconium silicate 12.62

The frit thus formed was quenched in water, and mixed with 7 parts of enamelers clay, part of anhydrous sodium sulfate, #3 part of bentonite, 44 parts of water and 10 parts of the same opacifier as in Example 13, per 100 parts by weight of frit. This mixture was milled to a fineness of less than 1 gram residue on a 200 mesh sieve. When sprayed on a panel and fired for 2 /2 minutes at 1520 F., this enamel showed a. reflectance of 76.7, as measured by the Hunter reflectometer, at an application rate of 72.0 gramsper sq. ft.

EXAMPLE The following ingredients (parts by weight) were mixed together and smelted in customary The frit thus formed was milled with the mill mixture and the slip fired on a panel as in Example 14. The enamel showed a reflectance of 70.8 at an application rate of 40.2 grams per sq. ft.

EXAMPLE 16 The following ingredients (parts by weight) were mixed together and smelted in customary fashion at 2050-2100 F.

Dehydrated borax 10.70 Quartz 37.13 Soda Mb 12.06 Sodium nitr 4.93 Zircon 17.00 Zinc oxide 1.48 Titanium oxide 6.90 Sodium silicofluoride 15.47 Amblygonite 2.59

The frit thus formed was milled with the mill mixture and the slip fired on a panel as in Example 14.

EXAMPLE 1'7 The following ingredients (given in parts by weight) were mixed together and smelted at 2150 F. until a melt forming smooth string results.

Dehydrated borax. ...1' 15.90

Sodium nitrate 5.00 Calcium carb nate 5.38 Zircon 7 7 Titanium dioxide 00 Sodium silicnflnm-idp 800 Amblyeonite Quartz 43 09 Soda fiQ'h 1 2 EXAIVIPLE 18 The following ingredients (parts by weight) were mixed and smelted together at a temperature' of 1900 F. until a melt forming smooth strings results.

Dehydrated borax 28.85 Pyrophyllite 40.00 Zircon--- 12.22

Sodium nitrate 3.50 Fluorspar 5.50 Cryolite 16.00 Amblyg ni 2.00 Soda ash 2.29

100 parts of this frit were milled dry with 2 parts of zirconium oxide opacifier to a fineness of about through a 200- mesh sieve. The milled mixture was dredged onto cast iron pieces and fired at 1550 F. for 1 minute. The enamel was a good white in color, of good opacity and luster.

In the above description and examples, when parts and percentages are mentioned, parts and percentages by weight are understood.

As many variations are possible within the scope of this invention, it is not intended to be limited except as, defined by the appended claims.

We claim:

1. The process of producing an enamel frit which comprises adding to the glass forming materials of the raw batch zirconium silicate and aluminum phosphate in such proportions that the mixture contains from 7 to 15 per cent zirconium silicate and from 0.25 to 4 per cent aluminum phosphate.

2. A frit composition for forming vitreous enamels, containing to 6 per cent amblygonite, together with a zirconium compound in such proportion that the frit contains 4 to 15 per cent zirconium'oxide.

3. A frit composition for forming vitreous enamels, containing 1 to 2 per cent amblygonite, together with a zirconium compound in such proportion that the frit contains 4 to 15 per cent zirconium oxide.

4. A frit composition for forming vitreous enamels, containing 1 to 2% per cent amblygonite, together with a zirconium compound in such proportion that the frit contains 6 to 12 per cent zirconium oxide.

5. A frit composition for forming vitreous enamels, containing to 6 per cent amblygonite, together with zircon in such proportion that the irit contains 4 to 15 per cent zirconium oxide.

enamels, containing 1% to 2 per cent amblygonite, together with zircon in such proportion that the frit contains 6 to 12 per cent zirconium oxide.

8. A frit composition for forming enamels, containing to 6 percent amblygonite, together with a zirconium compound in such proportion that the irit contains 6 to 12 per cent zirconium oxide.

9. A frit composition for forming vitreous enamels, containing to 6 per cent amblygonite, together with zircon in such proportion that the frit contains 6 to 12 per cent zirconium oxide.

LEON J. FROST. CHARLES H. COMMONS, JR.

vitreous I CERTIFICATE OF CORRECTION. Patent 'No. 2,559,260. January 18, 191414..

mon J. FROST,EI AL.

It is hereby certified that error appears 'in the printed specification of the above numbered patent. requiring correction as follows: Page 1, first coimn, line 9, for "Zirconifim silicate" reed --(zirconium silicate)"; line 11,9, after "much" insert --more--; and that the said Letters Patent should; be read with this correction therein that the Same may conform to the record of the case' in the Patent Office; Signedhnd seeled' this'lhth day of March, A. 1:. 19th.

' Leslie Frezer (Seal) Acting commissioner {of Patents. 

